If you want to get fit fast/lose weight can't advise you. There are so many (some contradicting) diets.

An operator should eat healthy, and high in calories. When you are active in the field combat rations are your breakfast lunch and dinner. Most countries have things similar to MRE's but often healthier and tastier. If you want I can post the contents of my combat rations. Just ask.

If you want to lose weight, you want to be in a caloric deficit — want to eat less calories than your resting calorie burn number. Cycling/swimming an hour or so seem to be great methods of burning calories. While walking an hour too burns quite a lot of calories, cycling/swimming does more. Try low-carb but high protein diet but make sure you mix in all of the nutrients because it's needed for your body.

If you want to maintain your weight, try to eat calories just around the number of your resting calorie burn amount and that is considering you're not that physically active.

You should try out other forums — particularly made for fitness — to get a better grasp. http://www.bodybuilding.com/ is a great start. You can also have a look around YouTube — many personal trainers/regular guys have started up channels to help people like you get fit.

Once you get a good grasp of how fitness generally is, you should be able to understand how to eat healthy, even as a tactical operator. As a matter of fact, you'll learn how to eat healthy in any situation. It's sort of making a good base for yourself and branching out from there.

This is to combined with an evening meal and provides 2400Kcal up to 3200Kcal depending on the extra nutrition. This is all you need to survive and remain active in combat, more calories are better in combat conditions, less are better when trying to lose weight.

This breakfast/lunch provides about 1900kcal per box, and 2700 with an issued dinner. in combat conditions no one cares about calories intake. 3000+ Kcal is fine, under harsh conditions.